An image forming apparatus such as a laser printer generally includes an optical scanner for exposing the surface of a photoconductor drum with light. As an example of a light source device provided in the optical scanner, a known light source device includes a light source (e.g., a semiconductor laser), a coupling lens (e.g., a collimating lens) for converting a laser beam into a beam of light, a barrel portion for supporting the light source, and a tubular holding member (e.g., a lens holder) for holding the coupling lens.
In a light source device, it is necessary to accurately position a light source and a coupling lens. To achieve this, for example, ultraviolet cure adhesive is applied to the outer peripheral surface of the barrel portion, and the holding member is inserted onto the barrel portion and then moved in both axial and peripheral direction to adjust the focal point of the coupling lens. Thereafter, the adhesive is irradiated and cured with ultraviolet light so that the positions of the light source and the coupling lens are fixed.
However, according to the conventional light source, the adhesive is coated on the outer peripheral surface of the barrel portion, and therefore the entire circumference of the barrel portion needs to be irradiated with ultraviolet light. This disadvantageously requires a time-consuming adhesive curing operation. Further, in order to accurately position the light source and the coupling lens, it is necessary that the adhesive be coated uniformly on the entire circumference of the barrel portion, which is not easy to perform.
In view of the above, it would be desirable to accurately and easily position the light source and the coupling lens.